<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        #d1,#d2{
            width:100px;
            height:100px;
            border:1px solid red;
        }
        #d1{
            margin-top:50px;
            margin-left:50px;
            margin-bottom: 50px;
            margin-right: 50px;
            /*四个方向*/
            margin:50px;
            /*上下20 左右50*/
            margin:20px 50px;
            /*上右下左 顺时针赋值*/
            margin:10px 20px 30px 40px;
        }
        #d2{
            /*外边距塌陷:
            1.兄弟元素上下相邻,彼此添加外边距取最大值
            2.父子元素上边缘重叠时,添加外边距会取最大值,会导致父子元素粘连到一起*/
            margin-top:20px;
        }
        #big{
            width:200px;
            height:200px;
            background-color: red;
            margin-top:100px;
            overflow:hidden;/*解决父子元素粘连问题*/
        }
        #big>div{
            width:50px;
            height:50px;
            background-color: green;
            margin-top:50px;/*左右边缘不存在粘连问题*/
            margin-left: 180px;
        }
        #s1{
            margin-right: 50px;
        }
        #s2{
            /*左右相邻彼此添加外边距,不存在外边距塌陷问题,所以是外边距相加*/
            margin-left: 50px;
        }

    </style>
</head>
<body>
<span id="s1">span1</span><span id="s2">span2</span>
<div id="big">
    <div></div>
</div>
<div id="d1">div1</div>
<div id="d2">div2</div>
</body>
</html>